阅读说明：本技术 一种壳聚糖/有序介孔碳电极材料制备方法及电催化应用 (Preparation method and electrocatalysis application of chitosan/ordered mesoporous carbon electrode material ) 是由 王欢 张婧杰 刘玉婷 杨丽荣 师怡 侯悦 陆嘉星 于 2020-07-09 设计创作，主要内容包括：本发明公开了一种壳聚糖/有序介孔碳电极材料制备方法及电催化应用,其特点是采用三嵌段共聚物为模板剂、木糖为碳源,利用简单、方便的水热法,经高温煅烧得到有序介孔碳；然后将丰富、廉价的天然生物高分子壳聚糖枝接到有序介孔碳上,从而制备出壳聚糖/有序介孔碳无金属电极材料,将其应用在环氧化合物与二氧化碳反应制备环状碳酸酯。本发明与现有技术相比具有电极材料不涉及重金属和贵金属,在环状碳酸酯的合成反应过程不涉及高温高压,电极材料易回收重复使用,且反应原子利用率高,原料绿色易得,对温室效应气体CO<Sub>2</Sub>进行了有效利用等优点,是一种具有应用前景的电极材料。(The invention discloses a preparation method and electrocatalysis application of a chitosan/ordered mesoporous carbon electrode material, which is characterized in that triblock copolymer is adopted as a template agent, xylose is adopted as a carbon source, and a simple and convenient hydrothermal method is utilized to obtain ordered mesoporous carbon through high-temperature calcination; then grafting abundant and cheap natural biological macromolecule chitosan onto the ordered mesoporous carbon so as to prepare the chitosan/ordered mesoporous carbon metal-free electrode material, and applying the chitosan/ordered mesoporous carbon metal-free electrode material to the reaction of an epoxy compound and carbon dioxide to prepare cyclic carbonate. Compared with the prior art, the invention has the advantages that the electrode material does not relate to heavy metal and noble metal, the high temperature and high pressure are not related in the synthetic reaction process of the cyclic carbonate, the electrode material is easy to recycle and reuse, the utilization rate of reaction atoms is high, the raw materials are green and easy to obtain, and the invention has the advantages of high greenhouse effect gas CO 2 To carry outHas the advantages of effective utilization and the like, and is an electrode material with application prospect.)

1. A preparation method of a chitosan/ordered mesoporous carbon electrode material is characterized in that triblock copolymer is used as a template agent of a mesoporous material, xylose is used as a carbon source, ordered mesoporous carbon is obtained by a hydrothermal method and high-temperature calcination, and then chitosan is grafted to the ordered mesoporous carbon, and the preparation method specifically comprises the following steps:

a. preparation of ordered mesoporous carbon

Mixing triblock copolymer F127, xylose and sulfuric acid with the mass concentration of 95-98% according to the weight ratio of 1: 0.5-1.5: mixing the raw materials in a mass ratio of 0.5-1.0, reacting at 120-150 ℃ for 18-26 h, carrying out suction filtration and washing on a reaction solution, drying to obtain a brown solid, and calcining the brown solid in a tubular furnace in a nitrogen atmosphere for 3-36 h to obtain ordered mesoporous carbon, wherein the calcining temperature is 300-800 ℃;

b. preparation of chitosan/ordered mesoporous carbon electrode material

Mixing chitosan and hydrochloric acid aqueous solution with pH =1 according to the weight ratio of 0.3-2.3 g: mixing 0.8-1.5L of the mixture in a mass-volume ratio to obtain solution A for later use; and c, mixing the ordered mesoporous carbon prepared in the step a with ethanol according to the weight ratio of 1 g: 0.1-0.5L massMixing the solution B in a volume ratio for later use; adding the solution A into the solution B dropwise, and then adding N₂H₄Stirring and mixing, reacting for 18-30 h at 50-90 ℃, centrifuging, washing and drying reaction liquid to obtain a product, namely the chitosan/ordered mesoporous carbon electrode material, wherein the solution A, the solution B and the solution N₂H₄The volume ratio of (A) to (B) is 8-20: 20-30: 2 to 4.

2. The method for preparing the chitosan/ordered mesoporous carbon electrode material as claimed in claim 1, wherein the temperature rise rate of the calcination is 1 ℃ per minute, the temperature is kept for 1.5-3 h when the temperature is raised from room temperature to 300-400 ℃, and the temperature is kept for 1.5-3 h when the temperature is raised to 500-800 ℃.

3. The electrocatalysis application of the electrode material prepared by the preparation method of the chitosan/ordered mesoporous carbon electrode material as claimed in claim 1, which is characterized in that the chitosan/ordered mesoporous carbon electrode material is used as a cathode of a one-chamber type electrolytic cell and a magnesium rod is used as an anode for electrocatalysis reaction of epoxy compounds for preparing cyclic carbonate, and the specific application comprises the following steps:

a. preparation of modified electrode

Mixing the prepared chitosan/ordered mesoporous carbon electrode material with 0.2-3% of sodium carboxymethylcellulose aqueous solution or styrene butadiene rubber aqueous solution according to the weight ratio of 1 g: mixing the carbon paper with the mass-volume ratio of 0.5-6.7 mL, coating the carbon paper on two sides of the carbon paper, and airing at room temperature to prepare a rectangular solid with the size of 2 cm multiplied by 1.8 cm as a modified electrode;

b. preparation of the electrolyte

Mixing epoxy compound, tetraethylammonium iodide and acetonitrile according to the weight ratio of 0.026-0.13: 0.015-0.045: mixing the mixture into electrolyte in a molar ratio of 10, and placing the electrolyte into a one-chamber electrolytic cell;

c. electrolytic reaction

Introducing CO into the electrolyte at normal pressure₂Until saturation, and at 1-20 mA/cm²The electrocatalytic reaction of the epoxy compound and the carbon dioxide is carried out at constant current density, the electrolysis temperature is 15-35 ℃, the electrolysis electric quantity is 0.5-3F per mol of propylene oxide, and F is a Faraday constant;

d. treatment of the reaction solution

Removing acetonitrile from the electrolytic reaction solution by rotary evaporation, adding 2M HCl, dissolving the rest substances in the reaction solution, extracting with diethyl ether for four times, combining organic phases, and extracting with anhydrous MgSO₄Drying for 1-2 h to obtain the product of cyclic carbonate.

Technical Field

The invention relates to the technical field of electrochemical organic synthesis, in particular to a preparation method of a chitosan/ordered mesoporous carbon electrode material and application of the chitosan/ordered mesoporous carbon electrode material in electrocatalysis synthesis of cyclic carbonate.

Background

Since the industrial revolution, the burning of fossil fuels has resulted in the worldwide emission of over 300 million tons of carbon dioxide per year. The increase in atmospheric carbon dioxide concentration not only has a major impact on global climate, but also leads to significant changes in our ecosystem. But it is also a renewable, non-toxic, low-cost, ideal C1 feedstock (Chen J, Jin B, Dai w, et al, Catalytic hydrolysis of CO)₂to cyclic carbonates overbiopolymerchitosan-grafted quarternary phosphonium ionic liquid as arecylablecatalyst[J]Applied Catalysis A: General 201448426-32.). With the rapid consumption of fossil fuels and the foreseeable "C1 crisis", the conversion of carbon dioxide into industrially useful chemicals has a dual meaning of environmental protection and sustainable chemistry. One of the most promising approaches in this field is the Cycloaddition of an epoxy compound and carbon dioxide to form cyclic carbonates [ Dai W, Mao J, Liu Y, et al, Commercial Polymer Microsphere Graded TBD-Based Ionic Liquids as effective and Low-CostCatalyst for the cyclic addition of CO₂with Epoxides[J]. Catalysis Letters,2019. 149:699–712]。

Epoxy compound and CO₂The formation of cyclic carbonates is of increasing interest, mainly due to the high atomic efficiency of the reaction, which are excellent aprotic polar solvents in synthesis and catalysis, and widely used as intermediates in the production of fine chemicals. In the prior art for synthesizing cyclic carbonate, the traditional organic method needs various catalysts and high-temperature high-pressure stripsAnd (3) a component. Yue at 120 deg.C under 1.5 MPa, the catalyst is [ APbim]I, the yield of propylene carbonate obtained is 89% [ C. Yue, D.Su, X.Zhang, W.Wu, L.Xiao, Amino-Functional Imidazolium Ionic Liquids for CO₂Activation and Conversion to Form Cyclic Carbonate,Catal. Lett., 144 (2014) 1313-1321.]. Peng et al at 140 ℃ under 2 MPa, the catalyst is BMImBF₄The yield of propylene carbonate obtained is 90% [ J. Peng, Y. Deng, cyclic addition of carbonic anhydride to propylene oxide catalyzed by ionic lipids, New J. chem., 25(2001) 639-641 ].]. Wu et al, at 100 ℃ 20 bar, with the catalyst Im-MnF, gave propylene carbonate with a yield of 57.91% [ Y.Wu, X.Song, J.Zhang, S.Xu, L.Gao, J.Zhang, G.Xiao, Mn-based MOFs as an effective catalyst for catalytic conversion of carbon dioxide cyclic carbonates and DFT students, chem.Eng.Sci., 201 2019) 288-.]. The electrodes commonly used in mild electrochemical methods are heavy metals such as Cu and Ag, and noble metals. Wu et al, under normal temperature and pressure, with heavy metal copper as cathode and 2.5F per mole of energization amount, gave propylene carbonate with a yield of 86% [ L, Wu, H.Yang, H.Wang, J.Lu, Electrosynthesis of cyclic carbonates from CO 2 ]₂andepoxides on a reusable copper nanoparticle cathode, RSC Advances, 5 (2015)23189-23192.]. Wu et al, under normal temperature and pressure, noble metal silver as cathode, 2F charge amount per mole, the yield of propylene carbonate obtained is 70% [ L, Wu, Electrosynthesis of Cyclic Carbonates from CO₂andEpoxides on Compacted Silver Nanoparticles Electrode, International Journalof Electrochemical Science, (2017) 8963-8972.]。

At present, no chitosan/ordered mesoporous carbon electrode material is used for electrocatalysis of CO₂Related art and literature reports on the preparation of cyclic carbonates.

Disclosure of Invention

The invention aims to provide a chitosan/ordered mesoporous carbon electrode material and application thereof in electrocatalysis synthesis of cyclic carbonate, aiming at the defects of the prior art, wherein a triblock copolymer is taken as a template agent of a mesoporous material, xylose is taken as a carbon source, and simple and easy processes are utilizedThe method comprises the steps of obtaining ordered mesoporous carbon through high-temperature calcination, grafting chitosan which is a natural biopolymer material and is rich and cheap onto the ordered mesoporous carbon, so that the prepared chitosan/ordered mesoporous carbon is a metal-free electrode material, and is applied to the application of preparing cyclic carbonate through the reaction of an epoxy compound and carbon dioxide, the reaction atom utilization rate is high, the raw materials are green and easy to obtain, and the cyclic carbonate is used for greenhouse effect gas CO₂Effectively utilizes the chitosan which is a biological macromolecule and has poor electrical conductivity, combines the chitosan with ordered mesoporous carbon with good electrical conductivity, and utilizes the chitosan to react with CO₂The prepared chitosan/ordered mesoporous carbon electrode material has large specific surface area, good conductivity and abundant active sites, obviously expands the application field and improves the catalytic activity, and is an electrocatalysis CO with application prospect₂Preparing the electrocatalytic material of the cyclic carbonate.

The technical scheme for realizing the purpose of the invention is as follows: a preparation method of a chitosan/ordered mesoporous carbon electrode material is characterized in that triblock copolymer is used as a template agent of a mesoporous material, xylose is used as a carbon source, ordered mesoporous carbon is prepared by adopting a hydrothermal method and high-temperature calcination, and then chitosan is grafted to the ordered mesoporous carbon, and the preparation method specifically comprises the following steps:

a. preparation of ordered mesoporous carbon

Triblock copolymer F127 was reacted with xylose and sulfuric acid in a 1: 0.5-1.5: 0.5-1.0, reacting for 18-26 hours at 120-150 ℃, filtering and washing reaction liquid by using ethanol, drying to obtain brown solid, calcining the brown solid in a nitrogen atmosphere tube furnace for 3-36 hours to obtain ordered mesoporous carbon, wherein the calcining temperature is 300-800 ℃, and the temperature rise procedure is as follows: raising the temperature from room temperature to 300-400 ℃ at a temperature raising rate of 1 ℃/min, keeping for 1.5-3 h, then raising the temperature to 500-800 ℃, and keeping for 1.5-3 h; the mass concentration of the sulfuric acid is 95-98%.

b. Preparation of chitosan/ordered mesoporous carbon electrode material

Mixing chitosan and hydrochloric acid aqueous solution with pH =1 according to the weight ratio of 0.3-2.3 g: mixing 0.8-1.5L of the mixture in a mass-volume ratio to obtain solution A for later use; and c, mixing the ordered mesoporous carbon prepared in the step a with ethanol according to the weight ratio of 1 g: mixing 0.1-0.5L of the mixture into a solution B for later use; adding the solution A into the solution B dropwise, and then adding N₂H₄Stirring and mixing, reacting for 18-30 h at 50-90 ℃, centrifuging, washing and drying reaction liquid to obtain a product, namely the chitosan/ordered mesoporous carbon electrode material, wherein the solution A, the solution B and the solution N₂H₄The volume ratio of (A) to (B) is 8-20: 20-30: 2 to 4.

The electrocatalysis application of a chitosan/ordered mesoporous carbon electrode material is characterized in that the chitosan/ordered mesoporous carbon electrode material is used as a cathode of a one-chamber electrolytic cell and a magnesium rod is used as an anode for electrocatalysis reaction of epoxy compounds for preparing cyclic carbonate, and the specific application comprises the following steps:

a. preparation of modified electrode

Mixing the prepared chitosan/ordered mesoporous carbon electrode material with 0.2-3% of sodium carboxymethylcellulose aqueous solution or styrene butadiene rubber aqueous solution according to the weight ratio of 1 g: and mixing the materials according to the mass-volume ratio of 0.5-6.7 mL, coating the mixture on two sides of carbon paper, and airing the mixture at room temperature to prepare a rectangular solid modified electrode with the thickness of 2 cm multiplied by 1.8 cm.

b. Preparation of the electrolyte

Mixing an epoxy compound with supporting salts tetraethylammonium iodide and acetonitrile according to the weight ratio of 0.026-0.13: 0.015-0.045: 10 molar ratio to be mixed into electrolyte, and the electrolyte is placed into a one-chamber type electrolytic cell.

c. Electrolytic reaction

Introducing CO into the electrolyte at normal pressure₂To saturation, at 1-20 mA/cm²The constant current density of the electrolytic solution is used for carrying out electrocatalytic reaction of the epoxy compound and the carbon dioxide, the electrolytic temperature is 15-35 ℃, the electrolytic capacity is 0.5-3F per mole of the epoxy compound, and F is a Faraday constant.

d. Treatment of the reaction solution

Removing acetonitrile from the electrolytic reaction solution by rotary evaporation, adding 2M HCl to dissolve the rest substances in the reaction solution, and extracting with diethyl ether for four timesCombining the organic phases and then using anhydrous MgSO₄Drying for 1-2 h to obtain the product of cyclic carbonate.

Compared with the prior art, the method has the advantages of high utilization rate of reaction atoms, green and easily-obtained raw materials, capability of avoiding high temperature, high pressure and complex catalyst in the traditional organic method, capability of avoiding the prior electrochemical method using heavy metal or noble metal as a cathode, economic and efficient organic synthesis of cyclic carbonate and greenhouse effect gas CO₂Effectively utilized, is an electrode material with good application prospect and CO₂A method for synthesizing cyclic carbonate.

Detailed Description

The present invention is further illustrated by the following specific examples.